Phase shifter circuit



y 1949. 5. M. OLIVER PHASE SHIFTER CIRCUIT" Original Filed Feb. 24, 1944 FIG.

I A A J u u w M l l r A .T 6 ddxw 2 s 7 0 w G1 a $55 2 T M 4 38%.. 4 0m u 2 v m w v u c 7 as: s a 3 aefiwl n m 5% 1/ P a z Li; a Wz ii lJ 1 ATTORNEY Patented July 19, 1949 PHASE SHIFTER CIRCUIT Bernard M. Oliver, New York, N. Y., assignorto Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Original application February 24, 1944, Serial No.

Divided and this application March 19, 1945, Serial No. 583,470

4 Claims.

This invention relates to phase shifting cir cuits and more specifically to such circuits for shifting the phase of input signals utilized in push-pull fashion. This application is a division of application Serial No. 523,721, filed February 24, 1944.

It is an object of this invention to provide an improved phase shifting circuit for balanced Waves.

It is another object of this invention to provide an improved circuit arrangement for shifting the phase of push-pull input signals by an angl less than 180 degrees, as for example, 99 degrees.

It is still another object of this invention to provide a novel circuit arrangement involving space current devices connected in push-pull relatio-nship.

In a specific embodiment of the invention,

given by way of example for purposes of illustration, there is provided a phase shifting circuit comprising two space current devices each having an anode, a cathode and a control element and means for applying between the con-- trol element and cathode of one of the devices a voltage wave which is substantially 180 degrees displaced from a voltage wave applied between the control element and cathode of the other device. Between the two cathodes are connected two current paths each comprising a resistance and capacity in series, one path being arranged so that the condenser thereof is connected to one of the cathodes and the elements in the other path being positioned so that the condenser is connected to the other cathode. Connections to an output circuit are made to the two terminals of the condensers remote from the cathodes to which they are respectively connected. When proper circuit constants are chosen for the elements in the two current paths, a balanced output wave shifted by 90 degrees from the corresponding input wave is obtained. An output wave of substantially the same phase as the input wave can also be obtained across terminals connected respectively to the two cathodes.

The invention will be more readily understood Fig. 1 is a diagram of a circuit ID for shifting the phase of push-pull input signals degrees. The circuit It comprises a double triode tube VI having input terminals II and I2 and output terminals. I3 and I4. The input signals, such as, for example, the two sine waves I93 and I04 (shown in Fig. 3) which are degrees displaced from one another, are applied to the input terminals and two sine waves I59 and I5 I, respectively, displaced by 90 degrees from the waves I03 and ice, are taken from the output terminals I3 and is. For a specific use in a radar system of sine waves having the phase displacements shown in 3, reference is made to the above-identified parent application.

Referring again to Fig. 1, the input waves I03 and are applied to the two control grids of the double triode tube VI which with its associated circuits acts to shift the phase of these two waves by 90 degrees. The two control grids are connected to ground through resistors I5 and I6, respectively, and the two cathodes are connected to ground through resistors I1 and I8 respectively. The two plates are connected to the positive terminal of. the direct current source I9 through resistor 20. Connected in parallel between the two cathodes of the tube VI are two series-connected circuits, one comprising the resistor 2! and the condenser 22 and the other comprising the condenser 23 and the resistor 24. The tube VI serves as a double cathode-follower tube to drive the phase shifter, and the outputs of this phase shifter are taken from the points C and D which are the respective common terminals of the two series-connected circuits just described. If desired, the output signals can be taken (without phase shift) from the terminals I3A and MA connected to the two cathodes.

The voltages applied to the tube VI result in alternating voltages from points A and B to ground which are equal and 180 degrees out of phase with each other. Since this is true, the voltage between points A and B will be twice that of the voltage between either of these points to ground. These voltages are shown in the vector diagram of Fig. 2 by vectors AG and GB and the voltage AB is the sum of these two vectors. In this diagram the point A is used as a reference point and, therefore, the arrows for vectors AG and BG are not shown 180 degrees apart as would be the case if point G or ground were used as a point of reference. The currents I1 and I2 flowing between points A and B by way of parallel paths ACE and ADB will lead the voltage AB by 45 degrees as shown on the vector diaon the drawings.

gram, since each of these paths has a resistance (21 or 24) in series with a capactive reactance of the same magnitude. For example, at 410 kilocycles this reactance is 3900 ohms. The voltage by the vector CB. The voltage drop Ecz across the condenser 22 lags behind current I2 by 90degrees and is represented by the vector AD. The voltage drop Em across the resistor 21 is in phase with the current I2 and corresponds to vector DB. The resulting voltage between C and D is 90 degrees ahead of the voltage AB. On the vector diagram of Fig. 2 the voltage from point C to ground adds to that from point D to ground so that vectors CG and DG are represented by arrows pointing upwards. However, if point G had been used as the reference point instead of point A, the vector GD would have been shown with the direction of the arrow reversed since the voltage from point C to ground is 180 degrees out of phase with that from point D to ground. The vector voltage at points C and D are then 90 degrees of the voltage AB at the cathodes of the tube VI and the voltage to ground at point C is 180 degrees out of phase with the voltage to ground at point D. The voltages from the points C and D are connected to any suitable push-pull amplifier. Circuit'constants of a phase shifting arrangement in accordance with the invention which has been actually constructed and satisfactorily operated in a radar system have been indicated It is to be understood, however, that'the invention is not limited to the use of elements having these particular circuit constants nor is the invention limited to use in radar systems. 3 Although the present invention has been described in terms of a preferred illustrative embodiment, it should be realized that the invention and its several features are susceptible of embodiment in a wide variety of other forms and hence the invention is to be understood as comprehending such other forms as may fairly come within the spirit and letter of the claims.

What is claimed is: t

1. In combination, two space current device each comprising an anode, a cathode and a control element, means for applying to each of said control elements a signal wave, the two waves being substantially identical except that they are displaced by 180 degrees, two series circuits connected in parallel between Said two cathodes,

4 each series circuit comprising a resistance and a condenser, all portions of each series circuit between said two cathodes being free to vary in potential and one circuit being arranged so that the condenser thereof is directly connected to one of said cathodes and the other circuit being arranged so that the condenser thereof is directly connected to the other of said cathodes, and

' means for connecting an output circuit to the two terminals of said condensers remote from said cathodes to which they are respectively connected, whereby the output waves are shifted in phase'from the corresponding input Waves.

2. In combination, twospace current devices each comprising an anode, a cathode and a control element, means for applyin to each of said control elements a signal wave, the two waves.

connected to the other of said cathodes, means for connecting an output circuit to the two terminals of said condensers remote from said cathode to which they are respectively connected, whereby the output waves are shifted in phase from the corresponding input waves, and means for connecting the terminals of a second output circuit to the two cathodes, respectively.

3. The combination of elements as in claim 1 in which the two resistances are equal andthe two condensersare also equal.

4. The combination of elements as'in claim 1 in which the two resistances are equal and the two condensers are of equal capacitance and have the same impedance at a predetermined frequency as the resistance, whereby the phase shift is degrees. l

BERNARD M. OLIVER.

REFERENCES CITED The followm' g references are of record in the file of this patent: 1

UNITED STATES PATENTS Number Name Date 2,135,051 Plebanski Nov. 1, 1938 2,201,345 Percival May 21, 1940 2,228,869 Chireix Jan, 14,1941 2,256,085 Goodale Sept. 16, 1941 2,376,392 Shepherd -Q. May 22, 1945 

